In recent years, a processing speed of a communication equipment and an information processing equipment becomes high, and particularly a transmission speed over 10 Gbps is requested in the case of backplane transmission. Similarly, a signal transmission speed between a line card and a switch card, which are used in a network apparatus, becomes high, and consequently limitation in a signal line length becomes strict in order to restrain a difference between the signal line lengths, and a signal loss.
FIG. 12 is a diagram showing composition of a backplane board of a general network apparatus. The general network apparatus includes two switch cards and a plurality of line cards mainly.
A line card 11 is equipped with a line interface like Ethernet, and is connected with another communication apparatus, PC, or the like. The line card 11 adds proprietary header information to a signal which is inputted from the line interface, and sends the signal, to which the proprietary header information is added, to a switch card 21.
The switch card 21 checks the header information which the line card 11 adds, and specifies a line card 11 which should provide an output of the network apparatus, and switches a path through the switch card 21, and sends the information to the line card 11 which should provide the output. The information, which is sent to the line card 11, is sent to another communication apparatus through the line interface.
Each signal line of each line card 11 is connected with two switch cards 21 through a connection on a backplane 31, and consequently the dual star topology is formed.
In recent years, a transmission speed between the line card and the switch card becomes high, and consequently limitation in the signal wiring length becomes strict in order to restrain the difference between the signal wiring lengths, and the signal loss. As a preceding art which realizes that high-speed transmission wirings have the same length, there is an art which is described in a patent literature 1 and a patent literature 2. The patent literature 1 and the patent literature 2 propose an art to make the difference between the wiring lengths null by arranging two boards, which are opposite each other, so that one board may be rotated by 90 degrees against the other board.
FIG. 13 is a diagram which is related to the patent literature 1 and which shows composition of a backplane board having implementation that one board out of two boards, which are opposite each other, is rotated by 90 degrees against the other board. FIG. 13 shows composition of a mutual connection apparatus, which can realize the same length wiring on a backplane board 1 with ease by making a logical circuit board 5 connected with the backplane board 1 vertically, and making a repeating board 2, which connects the logical circuit boards 5, connected with the backplane board 1 horizontally, and by assigning an area of a connector 6 of the logical circuit board 5, and an area of a connector 3 of the repeating board 2 properly.